Servovalve

ABSTRACT

The present disclosure provides a heat exchanger system for a servovalve, comprising a base comprising a supply port in fluid communication with a return port, a first passage for fluid connection to a source of cooling fluid, and a second passage in fluid communication with the return port. The system further comprises one or more pipes located over a surface of the base, the one or more pipes fluidly connected between the first passage and the second passage, such that in use cooling fluid may flow from the first passage to the second passage via the network of pipes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of the legally relatedU.S. Ser. No. 16/433,405 filed Jun. 6, 2019, which claims priority toEuropean Patent Application No. 18461586.2 filed Jul. 20, 2018, theentire contents of which are incorporated herein by reference in theirentirety.

FIELD

The present disclosure relates generally to a servovalve, and inparticular to a pneumatic servovalve for an aircraft in which a coolingsystem is employed to isolate the torque motor of the servovalve fromhigh temperatures, for example those that may be received from thesupply port of the servovalve.

BACKGROUND

FIG. 1 shows a conventional servovalve 10, which may comprise a housing12, a torque motor 14, and a pneumatic section 16.

The illustrated torque motor 14 is a conventional pneumatic torquemotor, comprising upper and lower permanent magnets 20, electromagneticcoils 22 and an armature 24. The armature 24 is held in place using atorsion bridge 26, which acts to bias the armature 24 to its restingposition as shown in FIG. 1. As is known in the art, upon application ofelectrical current to the electromagnetic coils 22, the armature ismoved or displaced from its resting position, which movement causes aflapper 28 to move or rotate.

The pneumatic section 16 of the servovalve 10 comprises a base 30, whichcomprises a supply port 32, a control port 34 and a return port 36 forpneumatic fluid. Movement of the flapper 28 as described above causesthe pneumatic fluid (e.g., air) to move through the pneumatic section 16from the supply port 32 to the return port 36.

The pneumatic fluid entering the base 30 of the servovalve 10 istypically very hot, such that the temperature of the supply fluid may besignificantly higher than ambient temperature. As such, heat may betransferred from the pneumatic fluid to the torque motor 14 via part ofthe base 30, as indicated by arrows 40.

It is desired to reduce the impact of heat transfer from the pneumaticsection 16 to the torque motor 14 of the servovalve 10.

SUMMARY

In accordance with an aspect of the disclosure, there is provided a heatexchanger system for a servovalve. The system includes a base comprisinga supply port in fluid communication with a return port, a first passagefor fluid connection to a source of cooling fluid, and a second passagein fluid communication with the return port. The system also includesone or more pipes located adjacent a surface of the base, the one ormore pipes fluidly connected between the first passage and the secondpassage, such that in use cooling fluid may flow from the first passageto the second passage via the one or more pipes.

The above construction insulates the base of the servovalve and canprovide improved cooling for any components that are positioned above(e.g., adjacent to and/or over) the one or more pipes (e.g., the one ormore pipes may be located between the base and the components).

The one or more pipes may be located near to and/or across the surfaceof the base, such that they are spread over the surface and in closeproximity thereto. The surface may be a substantially flat surfaceconfigured to support one or more components of a torque motor (e.g., asdescribed below).

A portion of the pipe or pipes may comprise a substantially flat layerof piping that is spread across the surface of the base and configuredto provide a layer of insulation between the base and any componentssituated over the base and/or fixed to the base.

The one or more pipes may comprise a labyrinthine pipe or pipes, whichmay increase the surface area coverage of the pipes across the base.

The one or more pipes may extend from an outlet of the first passagelocated in the surface of the base to an inlet of the second passagelocated in the surface of the base. The inlet and outlet portions of theone or more pipes may extend into or onto the surface of the base.However, it will be appreciated that the majority (e.g., over 90% of thepipes may form the substantially flat layer of piping referred to above.

The one or more pipes (e.g., the portion comprising the substantiallyflat layer) may extend substantially parallel to the surface of thebase. For example, the longitudinal axis of the one or more pipes inthis portion may remain substantially parallel to the surface of thebase.

The one or more pipes may extend over at least 30%, or even 50% of thesurface area of the surface of the base, to maximise the cooling abilitythereof.

The one or more pipes may be a single pipe fluidly connected between thefirst passage and the second passage. Using a single pipe may simplifythe construction of the heat exchanger.

The one or more pipes may be located at least above the supply port.This is commonly where the high heat fluid is passing through the base,and so locating the one or more pipes at least above this feature leadsto improved cooling as described herein.

In accordance with an aspect of the invention there is provided apneumatic servovalve comprising a heat exchanger system as described inany of the above embodiments.

The pneumatic servovalve may comprise a torque motor located over asurface of the base, wherein the one or more pipes are located betweenone or more components of the torque motor and the base. The torquemotor may be fixed to the surface of the base (e.g., using one or morefasteners).

The one or more pipes may be located between one or more components ofthe torque motor and the base. For example, the one or more pipes may belocated at least between a permanent magnet of the torque motor and thebase. In a further refinement, the one or more pipes may be located atleast between the portion of the base comprising the supply port and apermanent magnet of the torque motor.

Any aspect or embodiment of a heat exchanger system or pneumaticservovalve as described above may further comprise a layer of thermallyinsulating material located over (e.g., adjacent to and/or on) thesurface of the base. This has been found to further decrease heattransfer from the base to the components of a torque motor positionedthereon.

This aspect of the disclosure is considered to achieve technical effectsin its own right, and may be claimed independently, such that accordingto an aspect of the disclosure there is provided a pneumatic servovalve.The servovalve includes: a base comprising a supply port in fluidcommunication with a return port, a first passage for fluid connectionto a source of cooling fluid, and a second passage in fluidcommunication with the return port; a torque motor located over asurface of the base; and a layer of thermally insulating materiallocated over (e.g., adjacent to and/or on) the surface of the base tothermally insulate one or more components of the torque motor from thebase.

In any of the aspects or embodiments including the layer of thermallyinsulating material, the layer of thermally insulating material may beconfigured to rest against a permanent magnet of the torque motor,and/or may be configured to plug one or more gaps (e.g., air gaps)between the components of the torque motor and the base. The layer ofthermally insulating material may comprise or consist of mineral wool,for example ceramic fibre wool.

Additionally, or alternatively, a heat exchanger system or pneumaticservovalve as described above in any aspect or embodiment may furthercomprise one or more ceramic spacers located on the surface of the baseand configured to support one or more components of a torque motorthereon.

This aspect of the disclosure is considered to achieve technical effectsin its own right, and may be claimed independently, such that accordingto an aspect of the disclosure there is provided a pneumatic servovalve.The servovalve includes: a base comprising a supply port in fluidcommunication with a return port, a first passage for fluid connectionto a source of cooling fluid, and a second passage in fluidcommunication with the return port; a torque motor located over asurface of the base, wherein the torque motor is fastened to the baseusing one or more fasteners; and one or more ceramic columns, eachconfigured to surround a respective one of the fasteners.

In any of the aspects or embodiments including the ceramic columns, theceramic columns may comprise tubular members that each fit tightlyaround a portion of a respective fastener. Each ceramic column may beconfigured to support a component of the torque motor (e.g., a lowerpermanent magnet and/or pole piece) thereof.

In accordance with an aspect of the disclosure, there is provided amethod of using a heat exchanger system or pneumatic servovalve asdescribed above, in any aspect or embodiment, wherein the methodcomprises passing a cooling fluid through the one or more pipes suchthat cooling fluid flows from the first passage to the second passagevia the one or more pipes.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments will now be described, by way of example only, andwith reference to the accompanying drawings in which:

FIG. 1 shows a conventional arrangement for illustrative purposes only;

FIG. 2 shows an embodiment of the present disclosure;

FIG. 3 shows a close-up of part of the embodiment of FIG. 2;

FIG. 4 shows various cross sections of the embodiment of FIG. 2;

FIG. 5 shows a close-up of the embodiment of FIG. 2 illustrating somefeatures of the embodiment in use; and

FIG. 6 shows an exploded, cross-sectional view of the embodiment of FIG.2.

DETAILED DESCRIPTION

Herewith will be described various embodiments of a servovalve thatcomprises various features to assist in cooling the servovalve, andspecifically a torque motor thereof to mitigate the effects of heattransfer from the high-temperature pneumatic fluid flowing through theservovalve. The servovalve may be used in any suitable application, forexample as a servovalve for controlling aircraft working fluid such asengine bleed air or cabin air conditioning.

FIG. 2 shows a cross-section of a servovalve 100 according to anembodiment of the present disclosure. The servovalve 100 comprises ahousing 110, a torque motor 120, a pneumatic section 130 and aninsulating section 140.

The torque motor 120 may be a conventional torque motor, comprisingupper and lower permanent magnets 121, one or more electromagnetic coils122, an armature 123, a flapper 124, and a torsion bridge 125. The upperand lower permanent magnets 121 are located either side of the armature123, and with the electromagnetic coils 122 provide a magnetic circuitthat can be manipulated by supplying electrical current to theelectromagnetic coils 122. That is, application of an electrical currentto the electromagnetic coils 122 may cause the armature 123 to pivotagainst the action of the torsion bridge 125, which acts to move thearmature 123 into its resting position (as shown in FIG. 2). Movement ofthe armature 123 causes a corresponding movement of the flapper 124,which controls the supply of pneumatic fluid through the servovalve asis known in the art.

The torque motor 120 is contained within the housing 110, which extendsover and around the torque motor 120 to protect and isolate thecomponents of the torque motor 120 in use. In the illustrated embodimentthe housing 110 comprises a plurality of heat exchanger fins 112configured to transfer heat from the housing 110 to the externalenvironment. However, in various embodiments the housing 110 may beprovided without heat exchanger fins 112.

A cap 118 may be provided, which may be located over a top surface 119of the housing 110. The cap 118 may be configured to cover an aperture117 located in the top surface 119 of the housing 110.

The pneumatic section 130 of the servovalve 100 comprises a base 131,which comprises a supply port 132, a control port 134 and a return port136 for pneumatic fluid. The base 131 may be comprised of aluminium.Movement of the flapper 124 as described above causes the pneumaticfluid (e.g., air) to move through the pneumatic section 130 from thesupply port 132 to the return port 136.

As discussed above the pneumatic fluid passing through the supply port132 is typically relatively hot, and heat may be undesirably transferredfrom the pneumatic fluid through the base 131 as indicated by arrows 40.In order to mitigate or reduce heat transfer to the torque motor 120 andinsulation elements 140 is provided which comprises a number of partsconfigured to thermally isolate the components of the torque motor 120.

The torque motor 120 may be connected to the base 131 using one or morefasteners 126. The fasteners 126 may extend through part of the torsionbridge 125 and into the base 131 for securement thereto. The fasteners126 may comprise screws that cooperate with a corresponding screw threadwithin the base 131.

The base 131 may comprise a central column 139 that extends in adirection towards the torque motor 120, and which may be configured toreceive the flapper 124 of the torque motor 120.

FIG. 3 shows a cross-section of the servovalve 100 oriented at 90degrees to the cross-section shown in FIG. 2, and showing a close-up ofthe insulation elements 140.

The insulation elements 140 comprise three elements, any or all of whichmay be included in the servovalve 100 and various embodiments of thepresent disclosure in order to thermally isolate the torque motor 120.

A first of the elements is a layer 142 of insulating material, which maycomprise mineral wool, for example ceramic fibre wool. The layer 142 ofinsulating material may extend between an interior surface 114 of thehousing 110 and an exterior surface 115 of the central column 139 of thebase 131. The layer 142 may be configured to rest against one of thepermanent magnets 121 of the torque motor 120, and/or the insulatingmaterial in the layer 142 may be configured to plug one or more gaps(e.g., air gaps) between the components of the torque motor 120.

The types of mineral wool that can be used may be fire-resistant mineralwool such as ceramic fibre wool or kaowool. The layer 142 may be formedby sandwiching the mineral wool between aluminium sheets and compressingthe sheets together to condense the mineral wool into its desired shape.At this point, the mineral wool may then be inserted into the torquemotor during an appropriate stage of construction.

A second of the elements comprises one or more ceramic columns 144,which may be configured to surround the fasteners of the torque motor120 that secure it to the base 131. Using ceramic columns 144 has beenfound to provide improved thermal insulation and positioning of thetorque motor 120 when providing insulation elements 140 as describedherein, as well as providing a high compressive strength. It has beenfound that combining the first and second elements, namely the layer 142of insulating material and the ceramic columns 144 lead to improvementsin the thermal isolation of the components of the torque motor 120.

A third of the elements comprises a heat exchanger system in the form ofa labyrinthine pipe 146 that is located between the torque motor 120 andthe base 131 of the servovalve 100. In use a cooling fluid may betransmitted through the pipe 146 such that heat may be transferred fromthe base 131 of the servovalve 100 to the fluid within the pipe 146,rather than being transferred to the components of the torque motor 120.

FIG. 4 shows the heat exchanger system in more detail, and illustratesthe base 131 of the servovalve 100 in isolation with various componentsof the heat exchanger system, as well as the ceramic columns 144.

The heat exchanger system comprises an inlet 152 that forms the entranceto a first passage 154 within the base 131 of the servovalve 100 thefirst passage 154 extends from the inlet 152 to an outlet 155 in fluidcommunication with the pipe 146. The outlet 155 is located in an uppersurface 133 of the base 131. In the illustrated embodiment the pipe 146is formed by a single pipe, but in various embodiments additional pipesmay be provided that receive cooling fluid from the first passage 154.For example, the pipe 146 could be replaced by a network of pipes.

The pipe 146 leads to a second passage 156 located within the base 131which extends from an inlet 158 located in the upper surface 133 of thebase 131 to an outlet 150 in fluid communication with the return port136 of the servovalve 100.

The inlet 152 of the first passage 154 may be in fluid communicationwith a source of cooling fluid, for example ambient air. The coolingfluid may be drawn through the first passage 154, then the pipe 146 (ornetwork of pipes if applicable) and the second passage 156 by creatingsuction at the outlet 150 of the second passage 156. This section may becreated by any suitable means.

FIG. 5 illustrates an example of one particular means, which utilisesthe Venturi effect. That is, the second passage 156 is sized such that,upon activation of the servovalve 100 to transfer pneumatic fluid fromthe inlet port 132 to the return port 136, fluid passing through thereturn port 136 in the direction of arrows 170 creates a reducedpressure within the second passage 156. This draws the fluid containedwithin the second passage 156 and, in turn, the pipe 146 and firstpassage 154 into the flow of fluid passing through the return port 136as indicated at arrows 172.

As such, fluid will be transmitted from the source of cooling fluid influid communication with the first passage 154 and into the pipe 146 totransfer heat from the base 131 and improve the thermal isolation of thecomponents of the torque motor 120. Using this venturi method, from timeto time, for example if the return port 136 is closed, suction will notoccur. However, even if there is reduced or no suction, a layer ofstatic cooling air within the pipe 146 may still provide insulation andthermal isolation for the components of the torque motor.

It should be noted that the central column 139 of the base 131 may bethe primary cause of heat transfer from the base 131 (e.g., a main bodythereof) to the components of the torque motor 120. However, by usingone or more of the insulation elements 140 described above, inparticular the third element comprising a heat exchanger system and/orthe first and second elements in combination, thermal isolation of thetorque motor 120 will be improved. The embodiments described herein meanthat the torque motor 120 of the servovalve 100 is not exposed to hightemperatures, or has less exposure to the high temperature of thepneumatic fluid flowing through the servovalve 100. In addition, thetorque motor 120 may stay the same, or substantially similar to those ofthe prior art whilst incorporating the insulation elements 140 betweenthe torque motor 120 and the base 131 of the servovalve 100. In variousembodiments the heat exchanger system may be connected to ambient air asthe source of cooling fluid, and the means for drawing the cooling fluidthrough the heat exchanger system may not require substantial amounts ofenergy (e.g., using the venturi effect as discussed above).

FIG. 6 shows an exploded, cross-sectional view of the servovalve 100,from which it can be seen that the cap 118 may be secured onto the topsurface 119 of the housing 110 using one or more fasteners 218. Thehousing 110 may be located over the torque motor 120 and the insulationelements 140, including the pipe 146 ceramic columns 144 and layer 142of insulating material. These components then sit on top of the base 131of the pneumatic section 130, including the supply port 132 control port134 and return port 136.

Although the present disclosure has been described with reference tovarious embodiments, it will be understood by those skilled in the artthat various changes in form and detail may be made without departingfrom the scope of the invention as set forth in the accompanying claims.

1. A pneumatic servovalve comprising: a base comprising a supply port influid communication with a return port, a first passage for fluidconnection to a source of cooling fluid, and a second passage in fluidcommunication with the return port; a torque motor located over asurface of the base, wherein the torque motor is fastened to the baseusing one or more fasteners; and one or more ceramic columns, eachconfigured to support a respective one of the fasteners.
 2. Thepneumatic servovalve as claimed in claim 1, wherein the ceramic columnscomprise tubular members that each fit tightly around a portion of arespective fastener.
 3. The pneumatic servovalve as claimed in claim 1,wherein a ceramic column of the one or more ceramic columns isconfigured to support a pole piece of the torque motor.
 4. The pneumaticservovalve as claimed in claim 1, wherein a ceramic column of the one ormore ceramic columns is configured to support a permanent of the torquemotor.
 5. The pneumatic servovalve as claimed in claim 1, furthercomprising a layer of thermally insulating material located over thesurface of the base.
 6. The pneumatic servovalve as claimed in claim 1,further comprising a heat exchanger fluidly connected between the firstpassage and the second passage such that, in use, the cooling fluid isconfigured to flow from the first passage to the second passage via theheat exchanger and to be combined with the pneumatic fluid flowingthrough the pneumatic fluid return port
 7. A pneumatic servovalvecomprising: a base comprising a supply port in fluid communication witha return port, a first passage for fluid connection to a source ofcooling fluid, and a second passage in fluid communication with thereturn port; a torque motor located over a surface of the base; and alayer of thermally insulating material located over the surface of thebase to thermally insulate one or more components of the torque motorfrom the base.
 8. The pneumatic servovalve as claimed in claim 7,wherein the layer of thermally insulating material is configured to restagainst a permanent magnet of the torque motor.
 9. The pneumaticservovalve as claimed in claim 7, wherein the layer of thermallyinsulating material is configured to plug one or more gaps between thecomponents of the torque motor and the base.
 10. The pneumaticservovalve as claimed in claim 7, wherein the layer of thermallyinsulating material comprises a mineral wool.
 11. The pneumaticservovalve as claimed in claim 10, wherein the mineral wool comprises aceramic fibre wool.
 12. The pneumatic servovalve as claimed in claim 7,further comprising one or more ceramic spacers located on the surface ofthe base and configured to support one or more components of a torquemotor.
 13. The pneumatic servovalve as claimed in claim 7, furthercomprising a heat exchanger fluidly connected between the first passageand the second passage such that, in use, the cooling fluid isconfigured to flow from the first passage to the second passage via theheat exchanger and to be combined with the pneumatic fluid flowingthrough the pneumatic fluid return port.
 14. A pneumatic servovalvecomprising an integrated pneumatic fluid and heat exchanger system, thesystem comprising: a pneumatic fluid supply port in fluid communicationwith a pneumatic fluid return port to allow a pneumatic fluid leavingthe pneumatic fluid supply port to flow through the pneumatic fluidreturn port, a first passage for fluid connection to a source of acooling fluid; a second passage in fluid communication with thepneumatic fluid return port; and a heat exchanger fluidly connectedbetween the first passage and the second passage such that, in use, thecooling fluid is configured to flow from the first passage to the secondpassage via the heat exchanger and to be combined with the pneumaticfluid flowing through the pneumatic fluid return port.
 15. The pneumaticservovalve as claimed in claim 14, further comprising a torque motor,wherein the torque motor is located over a surface of the base, and theheat exchanger is located between one or more components of the torquemotor and the base.
 16. The pneumatic servovalve as claimed in claim 14,wherein the heat exchanger comprises one or more pipes located adjacenta surface of the base, the one or more pipes fluidly connected betweenthe first passage and the second passage, such that in use cooling fluidmay is configured to flow from the first passage to the second passagevia the one or more pipes
 17. The pneumatic servovalve as claimed inclaim 16, wherein the one or more pipes comprise a labyrinthine pipe orpipes.
 18. The pneumatic servovalve as claimed in claim 16, wherein theone or more pipes extend substantially parallel to the surface of thebase.
 19. The pneumatic servovalve as claimed in claim 14, furthercomprising one or more ceramic spacers located on a surface of the baseand configured to support one or more components of a torque motor. 20.The pneumatic servovalve as claimed in claim 14, further comprising alayer of thermally insulating material located over a surface of thebase.